Hi there! I just bought the game yesterday and I've been modding it furiously. But I don't know where certain files would go, like YAML files and such. .XNB files are straight forward, but some mods have .DLL files and other things and sometimes they don't explain where to put those files. I also cannot use the Mod manager Stardrop/Moddrop, because it gives me an error when I click on it.
YAML files should not go anywhere technically, they are a file that is supposed to be packed inside of XNB's, so if you download a YAML file the author didn't pack it correctly. .DLL files are probably SMAPI mods, you can go here: http://canimod.com/guides/using-mods#installing-smapi to learn how to install and use that.
There are currently 3 main types of mod: XNB mods, these are identified by the fact that they are a bunch of .xnb files, and *only* .xnb files - You can either install these by overwriting the correct file in your Content directory, or by using the `XnbLoader` SMAPI mod SMAPI mods, these are identified by the fact that they have a file called `manifest.json` *and* a `.dll` file - These are installed in their own sub-directories under Mods, and require you to have the SMAPI modloader installed Location Mods, these are identified by the fact that they have a `manifest.json` but no `.dll` file - These are installed in `Mods/AdvancedLocationLoader/locations/<moddir>` and require the `AdvancedLocationLoader` SMAPI mod
That looks like an error with SMAPI, or a mod that is using SMAPI. Did you install any mods manually or with ModDrop? If you installed the mods manually, try uninstalling the last few before relaunching the game. If you installed them manually I recommend removing them and using a mod manager moving forward.